The invention relates to a roll of the type having bending control, in which a hollow rotating roll having an outer working surface can be bent. The roll is provided with a non-rotatable crossbeam which penetrates the roll lengthwise, and is supported at its ends against an outer bracing element. The crossbeam is offset with a radial clearance all around from the inner circumference of the hollow rotating roll. Mounted on the crossbeam is a series or row of supporting elements that can be actuated by a fluid pressurized medium, fed by a plurality of supply lines running from the ends of crossbeam through a central longitudinal recess in the crossbeam. These enable the pressurization by the pressurized medium of individual or a plurality of supporting elements jointly connected group-wise to a supply line. The supply lines are being combined to make a supply unit that forms an assembly closed upon itself and which, as an entity, is insertable into or removable from the longitudinal recess of the crossbeam.
In rolls of this general type, a row of approximately twenty to eighty supporting elements are usually distributed over the length of the roll, usually on the side of the roll nip. These supporting elements are constructed like piston/cylinder units and abut against the inner circumference of the hollow roll, with bearing pockets being formed in the contact surface which exert a hydrostatic pressure against the inner circumference of the hollow roll, and from which pressurized fluid constantly escapes over their boundaries, so that a load-bearing liquid film is maintained which prevents a metallic contact between the supporting element and the inner circumference of the hollow roll.
During operation, these supporting elements must be supplied with at least one fluid pressurized medium. This medium usually is a pressurized fluid, in particular a pressurized oil, which may also be used as a heat-carrier medium. However, it is also possible to use gas-driven, and especially air-driven supporting elements.
Examples of such rolls are described in the following patents: U.S. Pat. No. 3,119,324, DE 22 30 139 B2, U.S. Pat. No. 2,395,915, DE 36 40 902 C2 and DE 38 20 974 C2, the contents of which are incorporated herein by reference for these teachings.
In many cases, the supporting elements are combined to form a plurality of groups which receive the fluid pressurized medium, at a common pressure, and thus require only one supply line. The smaller the groups, the more supply lines must be present. When, in the extreme case, each supporting element is to be acted upon separately in order to influence the line force in a particularly sensitive manner, at least just as many supply lines must be present as supporting elements. Since the supply lines cannot have less than a certain minimum cross-section, because the supporting elements need a certain throughput volume for their proper operation, especially for the maintenance of the separating liquid film, the feeding of the pressurized medium to the individual supporting elements or groups of supporting elements presents a problem, because only a very limited cross-section is available for this purpose. The crossbeam, which sags inside the hollow roll under the line load given by the line force, must not be substantially weakened in its bearing cross-section if the roll is to be able to generate higher line pressures.
A first possibility for supplying the supporting elements is the subject matter of the German patent 24 07 510 B2, in which, at the location of each supporting element, a control valve is provided, by means of which an actuating pressure adjusted for each supporting element is formed, by reduction, from the pressurized fluid introduced through a central main channel. For example, the respective valve is remotely pneumatically operated. Thus, correspondingly many remote-control lines must again be accommodated, as well. The arrangement of a multitude of valves is costly, and the weakening of the cross-section is not inconsiderable. A particular disadvantage, moreover, is that the valves are in the roll, so that in the event of a malfunction of even one valve, the entire roll must be dismantled.
In other specific embodiments, the valve arrangement is provided outside of the roll. In DE 26 57 061 C2 and DE 25 50 270 C3, one or a plurality of supply lines are formed, in the manner that adjustable compartmentalizations are provided in the longitudinal recess of the crossbeam, and the region between the individual compartmentalizations is supplied with pressurized medium through corresponding bore holes in the crossbeam or concentric pipe arrangements. The pressurized medium is then fed to the group of supporting elements, whose supply lines in the region between the respective compartmentalizations open through into the longitudinal recess. For higher numbers of supporting elements, or groups of supporting elements to be supplied separately, as occur, for example, in the roll according to the German utility model patent 93 14 568, such arrangements are unsuitable. In particular, the separation at the individual compartmentalizations is suitable only for relatively low pressures due to the limited serviceability of the sealing devices which must survive insertion and extraction.
This disadvantage is also true for the specific embodiment according to the German patent 28 47 029 B1, in which the supply lines into the regions between the individual compartmentalizations are formed by pipe lines. The pipe lines support the compartmentalizations. The entirety of pipe lines and compartmentalizations can be extracted as a unit out of the longitudinal recess of the crossbeam.
Thus, one of the problems to which the invention is directed is to provide a supply unit of this general type which is suitable for a greater number of supporting elements or groups of supporting elements to be supplied separately, and which can also be used at higher pressures.